The invention relates to the use of crosslinked polyvinylpyrrolidone as an additive to compact, particulate detergents and cleansers for the purpose of increasing the rate of disintegration thereof when brought into contact with water, to the particles of crosslinked polyvinylpyrrolidone having a particle size of from 50 to 400 .mu.m, to a process for the preparation of the compact, particulate detergents and cleansers, and to the compact, particulate detergents and cleansers themselves.
Dense or compact detergent and cleanser compositions are prepared by various agglomerating, compacting or pelletizing techniques. In the case of compact detergent and cleanser products present for example in the form of pellets, it is difficult to establish the correct balance between adequate strength properties and sufficiently rapid dissolution or disintegration thereof when subjected to the action of water. For example, detergent pellets which have been placed in the run-in chambers of a washing machine, must disintegrate over a period of less than one minute after being contacted with water. When there is only a slight degree of compaction of the detergent pellets a satisfactory rate of disintegration is achieved, in use, but frequently at the expense of the desired breaking resistance or abrasion resistance. Pellets thus prepared have only a small breaking resistance and tend to crumble and break to pieces during transport. On the other hand, excessive compaction or compression exerted during production of detergent pellets leads to unsatisfactorily long disintegration or dissolution times of the detergent pellets in use.
Compact or ultracompact detergents and cleansers are known, cf EP-A 340,013, EP-A 0,518,888, DE-A 19,649,560 and DE-A 19,649,565. In order to improve the rate of dissolution of particulate detergent formulations, use is made of solubilizing additives comprising, for example, copolymers of hydrophobic and hydrophilic monomers, such as copolymers of styrene and acrylic acid, cf WO-A 97/46657. According to the statements made in WO-A 97/46529 the rate of dissolution of particulate washing formulations is achieved by the use of, for example, addition products of ethylene oxide and/or propylene oxide and polyols.
Methods of producing pharmaceutical tablets reveal numerous possibilities for the preparation of pellets showing the desired strength properties and disintegration times. The main active mechanisms causing the disintegration of pellets are described to be wetting, capillary response (wicking) and swelling, cf Drug Development and Industrial Pharma, Vol. 6 (5) 511-536 (1980). Of the products which improve the solubility of tablets, mention has also been made of chemically crosslinked, swelling products such as microcrystalline crosslinked carboxymethylcellulose, crosslinked sodium carboxymethylstarch or crosslinked polyvinylpyrrolidone (cf Volker Buehler, Kollidon--Polyvinylpyrrolidone for the pharmaceutical industry, BASF, August 1993, pp 156 et seq).
By reason of the content of non-ionic surfactants and other low-melting wax-like, plastically deformable compositions in detergents, the addition of tablet bursters, which are known from pharmacy, to compact detergents and cleansers is rarely successful, particularly in the case of compact detergents used for washing laundry goods.
It is known that compact detergents and cleansers (shaped particles showing detergent and cleanser activity) have an increased rate of disintegration when they contain bursting agents in a special, granulated form, as are known in pharmacy and are capable of increasing the porosity or capillarity of the shaped particles and possess high adsorption capacity for water, DE 197 10 254 A1).
Compact detergents and cleansers prepared in this manner do indeed show an increased, but not sufficiently high, rate of disintegration, particularly in the case of compact detergents and cleansers which have been subjected to relatively high compacting pressures to increase their dimensional stability and breaking resistance. Furthermore, the thus prepared compact detergents and cleansers suffer from the drawback that the bursting agent must be converted to a granular form in an elaborate process step prior to compaction.